Circuit device for driving a squid magnetometric sensor and evaluating squid characteristics

Abstract

A circuit device for driving a SQUID magnetometric sensor. This device includes an FLL magnetometer circuit for driving the SQUID with an AC signal as a magnetometric sensor, an evaluator circuit for evaluating the SQUID characteristics, and a selector circuit for selecting a sensor function or an evaluator function. When the selection circuit selects one of the sensor and evaluator functions, only one of magnetometer and evaluator circuits is activated. Therefore, the circuit device can act alternatively as either a sensor or an evaluator.

We claim: 
     
       1. A circuit device for driving a magnetometric sensor comprising: a magnetometer circuit including a magnetic flux locked loop of magnetic flux modulation type for driving a SQUID as a magnetometric sensor;   an evaluator circuit for evaluating characteristics of the SQUID; and   a selector circuit for selecting a sensor function or an evaluator function,   said magnetometer circuit comprising a first input/output terminal for transmitting and receiving signals to and from the SQUID element, an AC signal source for producing an AC signal to drive the SQUID element and the magnetometer circuit, and a measurement terminal for providing a magnetic field measurement signal on the basis of a detected signal inputted from the first input/output terminal,   said evaluator circuit comprising a second input/output terminal for transmitting and receiving signals to and from the SQUID, an AC signal source for producing an AC signal to drive the SQUID and the evaluator circuit, and an evaluation terminal for providing a characteristics evaluation signal on the basis of the signal from the second input/output terminal, and   said selector circuit activating one of said magnetometer circuit and said evaluator circuit when said selection circuit selects one of the sensor function and evaluator function.   
     
     
       2. A circuit device as claimed in claim 1, wherein said selector circuit applies a supply voltage selectively to only one of said magnetometer circuit and said evaluator circuit when said selector circuit selects a corresponding one of the sensor function and the evaluator function. 
     
     
       3. A circuit device as claimed in claim 1, wherein: each of said first and second input/output terminals includes a transmitting terminal for exciting a coil combined with the SQUID;   the coil is provided to act as a feedback coil for applying a feedback magnetic field corresponding to the detected signal to the SQUID when the sensor function is selected; and   the coil is further provide to act as a magnetic field applying coil for applying a magnetic field for obtaining the SQUID characteristics to the SQUID when the evaluator function is selected.   
     
     
       4. A circuit device as claimed in claim 2, wherein: each of said first and second input/output terminals includes a transmitting terminal for exciting a coil combined with the SQUID;   the coil is provided to act as a feedback coil for applying a feedback magnetic field corresponding to the detected signal to the SQUID when the sensor function is selected; and   the coil is further provide to act as a magnetic field applying coil for applying a magnetic field for obtaining the SQUID characteristics to the SQUID when the evaluator function is selected.   
     
     
       5. A circuit device as claimed in claim 1, wherein: said first input/output terminal is formed by a connecter receptacle for receiving an end of a signal cable connected to the SQUID;   said evaluation terminal is formed by a connector receptacle for receiving an end of a signal cable connected to a graphic display; and,   when the evaluator function is selected, the characteristics evaluating signal appears on said evaluation terminal to display at least voltage vs. current and voltage vs. magnetic flux characteristics of the SQUID.   
     
     
       6. A circuit device claimed in claim 2, wherein: said first input/output terminal is formed by a connecter receptacle for receiving an end of a signal cable connected to the SQUID;   said evaluation terminal is formed by a connector receptacle for receiving an end of a signal cable connected to a graphic display; and,   when the evaluator function is selected, the characteristics evaluating signal appears on said evaluation terminal to display at least voltage vs. current and voltage vs. magnetic flux characteristics of the SQUID.   
     
     
       7. A circuit device as claimed in claim 3, wherein: said first input/output terminal is formed by a connecter receptacle for receiving an end of a signal cable connected to the SQUID;   said evaluation terminal is formed by a connector receptacle for receiving an end of a signal cable connected to a graphic display; and,   when the evaluator function is selected, the characteristics evaluating signal appears on said evaluation terminal to display at least voltage vs. current and voltage vs. magnetic flux characteristics of the SQUID.   
     
     
       8. A circuit device as claimed in claim 4, wherein: said first input/output terminal is formed by a connecter receptacle for receiving an end of a signal cable connected to the SQUID;   said evaluation terminal is formed by a connector receptacle for receiving an end of a signal cable connected to a graphic display; and,   when the evaluator function is selected, the characteristics evaluating signal appears on said evaluation terminal to display at least voltage vs. current and voltage vs. magnetic flux characteristics of the SQUID.   
     
     
       9. A circuit device as claimed in claim 1, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       10. A circuit device as claimed in claim 2, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       11. A circuit device as claimed in claim 3, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       12. A circuit device as claimed in claim 4, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       13. A circuit device as claimed in claim 5, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       14. A circuit device as claimed in claim 6, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       15. A circuit device as claimed in claim 7, wherein said SQUID is formed with an oxide type high-temperature superconductor. 
     
     
       16. A circuit device as claimed in claim 8, wherein said SQUID is formed with an oxide type high-temperature superconductor.